This application is based on European Patent Application No. 00830049.3 filed on Jan. 27, 2000, the content of which is incorporated hereinto by reference.
The present invention relates to a turbo-brush for cleaning a surface, such as, for example, a fabric surface, tapestry, furnishing, moquette, carpet and the like.
Generally, a turbo-brush comprises a rotating brush provided with bristles and actuated by a turbine with radial vanes. The rotating brush and the turbine are rotatably supported in two respective housings of a casing. The casing has a suction opening, inside which the rotating brush is placed, and a suction nozzle, located between the rotating brush and the turbine. A suction pipe, which is connected to a suction device, communicates with the suction nozzle and the turbine housing.
When the suction device is in operation, a flow of air, dust and other rubbish passes through the suction opening, the nozzle and the suction pipe and strikes the vanes of the turbine, causing the latter to rotate. The turbine transmits the rotary movement to the brush via a toothed belt, and the brush, rotating, with its bristles passes over the surface to be cleaned (fabric surface, which may be padded, tapestry, furnishing, moquette, carpet and the like), removing the dust and rubbish which are sucked up by the air flow generated by the suction device.
In turbo-brushes of this type, the turbine must supply the power necessary for overcoming the friction which is produced between the bristles of the brush and the surface to be cleaned, in addition to the friction which occurs between the shafts of the brush and the turbine and their support bearings.
The turbine supplies this power when the air flow passing through the suction nozzle strikes it with sufficient energy.
In order to exploit most efficiently the energy of the air flow, the vanes of the turbine must be struck by the whole flow discharged from the suction nozzle. For this purpose the turbine is usually positioned so that its bottom vanes are located opposite the nozzle outlet and so that their outer ends are very close to the bottom of the casing.
A drawback of this positioning of the turbine is the high aerodynamic noise level due to the intermittent interaction between the air flow leaving the nozzle and the turbine vanes.
In order to reduce this noise level, attempts have been made to increase the distance between the outer ends of the vanes and the bottom of the casing. In doing so, however, the turbine power is reduced.
The inventor has perceived that this reduction in power is due to the fact that a part of the air flow flows back inside the housing of the turbine without transmitting its energy to the said turbine and becomes a source of dissipation.
The object of the present invention is to reduce the noise level of a turbo-brush without adversely affecting the power supplied by the turbine.
The abovementioned object is achieved, in accordance with the invention, by means of a turbo-brush for cleaning a surface, comprising a casing provided with a suction opening, a rotating brush provided with bristles, a turbine which has a rotor provided with vanes and is operationally connected to said brush, a suction nozzle and a suction pipe connected to a suction device, said casing having a housing inside which said turbine is rotatably supported for rotating about an axis of rotation, said suction opening being located between said brush and said turbine for sucking a flow of air from said suction opening, direct it onto said brush and then towards said turbine, characterized in that said housing of said turbine has at least one lip projecting to a distance from an outer end of the vanes of said turbine which ranges from about 0.001% to about 0.1% of the diameter of said rotor of said turbine.
In particular, said distance ranges from about 0.002% to about 0.02% of the diameter of said rotor.
Preferably, said distance is about 0.002% of the diameter of said rotor.
Advantageously, said at least one lip is located at an angle which ranges from about xe2x88x9260xc2x0 to about 180xc2x0 with respect to an axis parallel to a surface to be cleaned, having its origin on the axis of rotation of said turbine and directed towards said brush, the angles measured in the opposite direction with respect to the direction of rotation of said turbine being positive.
Preferably, said angle ranges from about xe2x88x9240xc2x0 to about 130xc2x0.
Advantageously, said angle is about 1xc2x0.
According to a variation, said angle is about 120xc2x0.
Advantageously, said housing of said turbine has two lips projecting to the abovementioned distance from the outer end of said vanes, said two lips being located at respective angles which range from about xe2x88x9260xc2x0 to about 180xc2x0 with respect to an axis parallel to a surface to be cleaned, having its origin on the axis of rotation of said turbine and directed towards said brush, the angles measured in the opposite direction with respect to the direction of rotation of said turbine being positive.
Preferably, said two lips are located at respective angles which range from about xe2x88x9240xc2x0 to about 130xc2x0 with respect to said axis parallel to the surface to be cleaned.
In particular, said two lips are located, one at an angle of about 20xc2x0 and the other at an angle of about 45xc2x0 with respect to said axis parallel to the surface to be cleaned.
Advantageously, said turbo-brush comprises an acoustic damper associated with said housing of said turbine, said acoustic damper having a predefined volume and being connected to said housing of said turbine by means of a baffle provided with a predefined number of holes having predefined dimensions, said volume, said number of holes and their dimensions having values such as to dampen at least one predefined acoustic frequency.
Preferably, the volume of said acoustic damper ranges from about 1% to about 20% of the overall volume of said turbine, and said holes have a diameter which ranges from about 0.5 mm to about 5 mm and a length which ranges from about 0.5 mm to about 4 mm and consist of a number which ranges from 1 to 100.
In particular, the volume of said acoustic damper is about 7% of the overall volume of said turbine, and said holes have a diameter of about 2.5 mm and a length of about 1.5 mm and consist of a number equal to 35.
Advantageously, said baffle has a porosity, understood as being the ratio of voids to solid areas, which ranges from about 1% to about 50%.
Preferably, said porosity ranges from about 5% to about 20%.
Advantageously, said damper has a height, measured with respect to the line of intersection between said baffle and a plane of longitudinal cross section, which assumes values inversely proportional to the frequencies to be dampened.
Preferably, said damper has a height which ranges from about 1 to about 30 mm.
In particular, said height ranges from about 6 to about 12 mm.
Advantageously, said suction nozzle has an elongation ratio b/h, between width b and height h, which ranges from about 3 to about 7.
In the turbo-brush according to the invention, the use of one or two lips which project from the housing of the turbine and which are very close to the outer ends of the turbine vanes constitutes a very effective obstacle to the formation of an air flow recirculating between the top part of the turbine and its housing. Therefore, it is possible to exploit all the energy which is contained in the air jet which strikes the turbine and obtain from it the maximum power.
As a result of this, a space suitable for absorbing the noise may be left around the turbine. In fact, in the turbo-brush according to the invention it is possible to arrange the outer ends of the vanes at a distance from the turbine housing, except for the lip zones, without adversely affecting the performance of the turbine in view of the absence of a recirculating flow.
Moreover, the acoustic damper connected to the turbine housing may be provided with dimensions suitable for damping the most troublesome acoustic frequencies. Therefore, it may be a multiple, i.e. it may silence more than one frequency, thus making it possible to achieve a significant reduction in the noise produced by the turbine.